Actually it's not. The saucer when seperated has the impulse engines in the perfect spot. When connected the nozzles would have to be trimmed to prevent what would otherwise produce a strong nose down tendency.

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You are assuming - with absolutely no justification - that the warp nacelles along with the segments of the pylons located above the impulse engine thrust line are substantially lighter than the secondary hull, interhull adapter and the pylon segments located below the impulse engine thrust line.

Actually it's not. The saucer when seperated has the impulse engines in the perfect spot. When connected the nozzles would have to be trimmed to prevent what would otherwise produce a strong nose down tendency.

When connected the reverse thrust location right under the torpedo tube would be quite good.

Of course, the fact that the ship has no reverse thruster on the saucer when a saucer seperation could happen is not a good design feature.

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If you assume like I do that the ship channels its impulse exhaust through a subspace field anyway, the impulse engines can be anywhere on the ship you want them to be; the only thing you need is a space in which to bend the exhaust stream in a particular direction so its final vector goes through the center of mass.

This may or may not explain why Federation starships are built the way they are. After all, why would you have your gigantic warp nacelles and modules on the end of really long pylons when you could just build ALL of your ships like the Defiant, i.e. a dense flying brick of starship with nothing sticking out or exposed? The separation gives you more directions you can bend your impulse exhaust which in the end makes the ship more maneuverable at sublight speeds.

Actually it's not. The saucer when seperated has the impulse engines in the perfect spot. When connected the nozzles would have to be trimmed to prevent what would otherwise produce a strong nose down tendency.

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You are assuming - with absolutely no justification - that the warp nacelles along with the segments of the pylons located above the impulse engine thrust line are substantially lighter than the secondary hull, interhull adapter and the pylon segments located below the impulse engine thrust line.

TGT

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From the way they're positioned, the warp nacelles and the upper pylon supports would have to account for something like 90% of the ship's total mass for the center of gravity to be that high. Are we looking at a 70,000 ton ship with a pair of 500,000 ton warp nacelles attached to it? Each seperate warp coil would have to weigh as much as the Titanic.

Well, the problem with Rick's answer is that the word "impulse" isn't just a made-up word. It's a real, technical, scientific word with a real, technical, scientific meaning. And that meaning is so clear, so specific, and so unambiguous that there's no room for redefinition.

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But that sounds like so much nonsense. Booting of computers has nothing to do with footwear, the gas in automobile gas tanks is not gaseous (and indeed nonsense terminology like "liquid gas" is in regular use), and a fission bomb or even a napalm bomb is considered a kinetic weapon. Against this background, it would be absurd to insist that the iconic drive system of starships would have to hold on to some specific meaning of the word being used as its name.

From the way they're positioned, the warp nacelles and the upper pylon supports would have to account for something like 90% of the ship's total mass for the center of gravity to be that high. Are we looking at a 70,000 ton ship with a pair of 500,000 ton warp nacelles attached to it? Each seperate warp coil would have to weigh as much as the Titanic.

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Which in fact sounds rather attractive. That way, Scotty's "nearly a million gross tons" would make perfect sense for a ship whose hull weighs in at 180,000 tons or so.

Of course, this solves absolutely nothing as regards the subject of this thread, because the impulse engines of the Reliant would then in turn be located in a Newtonially unworkable location.

Well, the problem with Rick's answer is that the word "impulse" isn't just a made-up word. It's a real, technical, scientific word with a real, technical, scientific meaning. And that meaning is so clear, so specific, and so unambiguous that there's no room for redefinition.

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But that sounds like so much nonsense. Booting of computers has nothing to do with footwear, the gas in automobile gas tanks is not gaseous (and indeed nonsense terminology like "liquid gas" is in regular use), and a fission bomb or even a napalm bomb is considered a kinetic weapon. Against this background, it would be absurd to insist that the iconic drive system of starships would have to hold on to some specific meaning of the word being used as its name.

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"Booting" and "gas" are both shorthand terms that are shortened from longer or related terms. "booting" in computers comes from the term "bootstrapping," which means using a simple system to activate a more complex system. "Gas" is a shortening of "gasoline" which specifically refers to a petroleum product.

"Impulse" is already a term used in aerospace engineering and spacecraft propulsion in the same way "bootstrapping" already had connotations of someone or something performing a complicated process through simple means without external help.

From the way they're positioned, the warp nacelles and the upper pylon supports would have to account for something like 90% of the ship's total mass for the center of gravity to be that high. Are we looking at a 70,000 ton ship with a pair of 500,000 ton warp nacelles attached to it? Each seperate warp coil would have to weigh as much as the Titanic.

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Which in fact sounds rather attractive. That way, Scotty's "nearly a million gross tons" would make perfect sense for a ship whose hull weighs in at 180,000 tons or so.

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And then you'd have to postulate verterium cortenide or whatever Enterprise is using as being some kind of ultra-dense material such that a chunk of it the size of a football would weigh as much as a compact car. I don't really disagree with this in principle, just that the logistics of working with material this dense and this heavy aren't well represented in the Trekiverse (and didn't we see some shuttlecraft lifting warp coils out of Voyager's warp nacelle once?)

Of course, this solves absolutely nothing as regards the subject of this thread, because the impulse engines of the Reliant would then in turn be located in a Newtonially unworkable location.

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Same case for the E-D, whose impulse engine is slightly below the nacelles, or NX-01 whose nacelles are well above centerline, or runabouts and shuttlecraft whose engines are nowhere near in line with the nacelles (given the same material, a single warp coil would weigh more than the entire rest of the shuttlecraft). Any way you play it, you're going to need something to curve the exhaust plume so it thrusts through the ship's center of mass.

"Booting" and "gas" are both shorthand terms that are shortened from longer or related terms. "booting" in computers comes from the term "bootstrapping," which means using a simple system to activate a more complex system. "Gas" is a shortening of "gasoline" which specifically refers to a petroleum product.

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So "impulse" could perfectly well be a similar shortening. Just because it also remains in use in a different meaning is irrelevant, as "boot" and "gas" also do.

I don't really disagree with this in principle, just that the logistics of working with material this dense and this heavy aren't well represented in the Trekiverse (and didn't we see some shuttlecraft lifting warp coils out of Voyager's warp nacelle once?)

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Well, warp coils are the most magical part of starship construction anyway, so maximizing the magic doesn't sound like a bad idea.

And shuttles can travel at warp two or go from planet to planet in a matter of hours or minutes. Lifting a chunk of neutronium-unobtainium doesn't sound like asking too much of those engines... (That was in VOY "Nightingale", FWIW.)

Any way you play it, you're going to need something to curve the exhaust plume so it thrusts through the ship's center of mass.

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If it even needs to do that. The exhaust plume of a Chevrolet Corvette does not.

There are starships with impulse engines that seem to blast right into their own pylon structures, such as the ENT Intrepid or the Steamrunner. Perhaps there is no jet of exhaust associated with an impulse nozzle, just a warm puff of waste matter being vented in a random direction every now and then. The drive could still combine "field propulsion" and pseudo-rocketry, but the rocket exhaust would be generated in some manner unrelated to the nozzles. Perhaps there's a giant virtual "thrust chamber" being generated out of forcefields, well aft of the ship, or forward if need be - kilometers wide, of variable shape, the works...

"Booting" and "gas" are both shorthand terms that are shortened from longer or related terms. "booting" in computers comes from the term "bootstrapping," which means using a simple system to activate a more complex system. "Gas" is a shortening of "gasoline" which specifically refers to a petroleum product.

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So "impulse" could perfectly well be a similar shortening. Just because it also remains in use in a different meaning is irrelevant, as "boot" and "gas" also do.

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No, because "bootstrapping" means roughly the same thing in computer science as it does in vernacular. There is no similar term in computer science or mathematics that has a different meaning. Similar to the term "gasoline" which has been in use since at least the 19th century and has no similar term with which it may be confused (in fact, even "natural gas" as a fuel source is generally referred to as "CNG" for precisely this reason).

"Impulse" could be an acronym, as in "IM-Pulse" or something, but it's too late to redact that since so far it's always been written as the conventional word and, on a few occasions, has actually been USED in the conventional newtonian sense.

There are starships with impulse engines that seem to blast right into their own pylon structures, such as the ENT Intrepid or the Steamrunner.

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Which would be a bad design even if impulse engines merely vented exhaust non-propulsively. Not so if the ship has a system inherent in the engine to control what path the exhaust plume takes as it leaves the nozzle.

Perhaps there is no jet of exhaust associated with an impulse nozzle, just a warm puff of waste matter being vented in a random direction every now and then. The drive could still combine "field propulsion" and pseudo-rocketry, but the rocket exhaust would be generated in some manner unrelated to the nozzles. Perhaps there's a giant virtual "thrust chamber" being generated out of forcefields, well aft of the ship, or forward if need be - kilometers wide, of variable shape, the works...

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Perhaps the impulse engine propels the ship by rapidly breeding tribbles and then beaming them into deep space where their shrill cries for help cause an impulsive reaction in the ship's improbability field?

Or maybe impulse engines work pretty much the way they're implied to work, as technobabble rocket engines that use "driver coils" to overcome the inevitable restrictions of Jon's Law?

The exhaust plume of a Corvette cannot be used to push the car forward if you put the gearshift in neutral. Impulse engines can.

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According to whom?

Quite to the contrary, it appears that a starship at full stop (say, relative to an adversary ship floating off her bow) can still perfectly well have her impulse engine glowing just as madly as when at "full impulse".

Or maybe impulse engines work pretty much the way they're implied to work, as technobabble rocket engines that use "driver coils" to overcome the inevitable restrictions of Jon's Law?

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It might help if the implication were explicated at some point. We have a conspicuous lack of references to rocketlike behavior of impulse engines in onscreen material. Instead, impulse typically seems to behave like a maritime propeller system, free of propellant even if needing fuel, and governed by the need to maintain power for steady speed.

The idea of there being a rocket component to impulse engines is something that can be made to work with suitable effort. Such a component is not an onscreen necessity, though.

The exhaust plume of a Corvette cannot be used to push the car forward if you put the gearshift in neutral. Impulse engines can.

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According to whom?

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TNG "Booby Trap" the impulse engines were used--apparently without their driver coils--to accelerate the Enterprise to inertial flight at over a hundred meters per second. Apparently the subspace/warp fields used for propulsion were what the aceton assimilators were reacting to in order to hold the ship in place, so using the impulse engines without the field-effect boost reduced them to old-fashion rocket engines.

From the same episode you find that the "glow" continues in the engine even after it is shut down, as it does on the saucer in "Best of Both Worlds" despite the fact that the impulse engines are said to be damaged. Considering the impulse engines are powered by fusion reactors and double as a power source for the ship, I'd be a little alarmed if they STOPPED, glowing even when the ship was at rest.

Or maybe impulse engines work pretty much the way they're implied to work, as technobabble rocket engines that use "driver coils" to overcome the inevitable restrictions of Jon's Law?

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It might help if the implication were explicated at some point.

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See above. And also check out Scotty's line in "Relics" where he mentions that the ion trail from Enterprise' engines is indicative of "an impulse engine at full reverse." This is clearly technobabble, but the implication here is that impulse exhaust behaves differently depending on what direction you're trying to go, something that could ONLY be explained by a propulsive effect by the exhaust.

The idea of there being a rocket component to impulse engines is something that can be made to work with suitable effort. Such a component is not an onscreen necessity, though.

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One removes that component only with copious amounts of handwavium and fanciful thinking which in this case is not warranted. One might as well pick up a coke bottle and say "This could be described as a coke bottle with a suitable effort, but it could just as easily be a flux capacitor from the 35th century."

And also check out Scotty's line in "Relics" where he mentions that the ion trail from Enterprise' engines is indicative of "an impulse engine at full reverse." This is clearly technobabble, but the implication here is that impulse exhaust behaves differently depending on what direction you're trying to go, something that could ONLY be explained by a propulsive effect by the exhaust.

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No, there are more ways to explain it actually, the exhaust coming from the fusion engines will form a plume in a certain way and shape, if you're on full impulse forward and you're dragged ass first towards the dyson sphere then your ship will pass through the gas its belching out making quite a nice pattern which a computer of any kind in the 23th/24th century can distinguish, this still doesn't have to mean that the exhaust of the fusion reactors has anything to do with the propulsion method of the impulse engines themselves.

Cary, is there any reason the thrust or force applied over time can't be non-newtonian in impulse engines? That is, produced without tossing something out of a combustion chamber?

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Because thrust itself is a newtonian action and cannot be applied without an equal and opposite reaction....

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So, assuming the EmDrive actually works (and I have no interest in debating whether it does or not -- just assume for the purposes of argument that it does), you're claiming it doesn't apply force over time just because it doesn't expel reaction mass?

I'm looking at my copy of Star Trek: The Motion Picture - 14 Official Blueprints (Wallaby Books, 1980) right now and those particular features are completely unmarked in all three sheets that depict the NCC-1701 Refit's exterior.

TGT

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Confirmed. Those features are unlabeled.

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Hmmm... I'll have to go back and see if I can figure out what, then, I was thinking of. I'm sure I knew that's what they were waaaay back then. (In the first TMP E model I built, I even put "burn marks" trailing from those, because I'd read in something official that they were dockyard-maneuvering thrusters).

Still... suppose that I can't find whatever it is. What do you guys think that they are? And claiming "deuterium fill ports" is just silly... there's no possible engineering argument for a "fill port" to be designed like that, is there? I mean... that's not a "new magic technology," it's a basic design element which would be no different than what we have today. Most likely, a "fill port" would resemble, quite closely, what you have on your car's gas tank - a cover plate which can swing aside to reveal the "plumbing" underneath.

Cary, is there any reason the thrust or force applied over time can't be non-newtonian in impulse engines? That is, produced without tossing something out of a combustion chamber?

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Because thrust itself is a newtonian action and cannot be applied without an equal and opposite reaction....

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So, assuming the EmDrive actually works (and I have no interest in debating whether it does or not -- just assume for the purposes of argument that it does), you're claiming it doesn't apply force over time just because it doesn't expel reaction mass?

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If it does apply force over time it has to have something to apply that force ON. I could buy something that interacts with and pushes against Earth's electromagnetic field, but but in order to apply force you need to have something to push on at least. Basically, no matter how strong you are, you can't life a rock if you're standing on it.

Because thrust itself is a newtonian action and cannot be applied without an equal and opposite reaction....

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So, assuming the EmDrive actually works (and I have no interest in debating whether it does or not -- just assume for the purposes of argument that it does), you're claiming it doesn't apply force over time just because it doesn't expel reaction mass?

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If it does apply force over time it has to have something to apply that force ON. I could buy something that interacts with and pushes against Earth's electromagnetic field, but but in order to apply force you need to have something to push on at least. Basically, no matter how strong you are, you can't life a rock if you're standing on it.

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I get you ... and that makes sense. But let's assume a mystery reaction. We don't know what we're acting against. We only know, when we push this button, that light comes on, the big box on the back of the ship starts buzzing, and the ship starts moving forward. Darned if we know how it's doing what it's doing, but the ship is definitely moving. Since we know the mass of the ship, can measure its change in velocity relative to something (otherwise we wouldn't know we were moving), and can measure the passage of time, don't we know the drive's force over time?

Which brings me full-circle back to the (misunderstanding?) that led me to question Cary in the first place on this issue: all we really know about impulse engines is that they exert a force on the ship that causes them to move. Even if the force is provided by super-science reactionless drive systems, they're still essentially impulse engines.

Mind you, I say all this while still being a proponent of the impulse-engines = refined fusion drive. I'm just a little fuzzy on why impulse-engines must involve expelling a reaction mass.

I know what i'm about to say is canon-heresy, but Impulse Engines see to be used differently in TOS than in the movies and later series.

In the Original Series, the Impulse Drive seems to be more of an auxiliary propulsion that gets the ship moving on simple newtonian physics if their magic warp drive fails.

They don't usually refer to the Impulse Engines when the Warp Drive is functioning, we get orders like "Sub-Light one half" in Friday's Child, or references to the Enterprise "warping out of orbit" in the Menagerie. It is my impression that the Warp Drive, at least as it was established in TOS was the starship's main propulsion and was used for sublight propulsion as well as interstellar travel.

This is all irrelevant now since the Impulse Engines were later retconned to be the ship's main propulsion at sublight speeds, but I don't think this was the original intent.

Since while we're rebooting the Enterprise and everything else anyway, I'd like to bring back this concept of the warp drive being able to handle sublight propulsion as well, and relegating archaic impulse engines to being used as an auxiliary, thus no longer need to figure out magical ways a Newtonian impulse engine can stop or reverse a starship's velocity without producing any forward thrust.

Sounds good. Indeed, "impulse engines" in TOS often sounded more like an alternate or auxiliary way to channel power to the propulsion devices, rather than being a category of propulsion devices themselves. Kirk would at times add the output of the impulse engines to that of the warp engines, the way a modern frigate captain might order the output of the cruising diesel engines to be added to that of the dashing turbine engines or vice versa. All that output goes to the same set of propellers, no matter how the combination of engines is chosen...

That naval analogy might be taken to hold throughout: an "engine" would be a power production system, be it a fusion-powered "impulse" engine or an antimatter-powered "warp" engine. The output of the engine would be channeled to a propulsion system, which could be either two sets of warp coils in two big outriggered nacelles, or two such big sets plus a smaller set at the aft rim of the saucer. A bit like main propellers and steering/trolling propellers on a modern ship.

Different ships from different eras would have different balances between these power and propulsion systems. One might even argue that only those ships with the intriguing blue domes or squares on the saucer aft rim have actual "impulse coils" which do this subspace mass reduction magic thing all on their own (NX-01, NCC-1701-A, B and D), while those ships without such domes (the TOS NCC-1701, perhaps NCC-1701-C and E) channel the output of their impulse engines into the big nacelles for generation of mass reduction fields for sublight propulsion, and perhaps for the occasional faster-than-light foray...